1. Field of the Invention
The present invention relates to a transmission gear shift system in which a shift select shaft supported on a transmission case is maintained in a central select position among three select positions in the axial direction by means of the resilient force of a select spring.
2. Description of the Prior Art
A transmission gear shift system is known in Japanese Patent Publication No. 2629871. The shift select shaft of this gear shift system is placed between a shift lever which is operated by the driver and shift forks for selectively establishing a plurality of gear shift stages and moves in the axial direction in operative connection with a select operation of the shift lever and rotates according to a shift operation of the shift lever. The shift select shaft can stop in three select positions by moving in the axial direction, and it is forced by two select springs to be maintained in a central select position when the shift lever is in a neutral position. When the shift select shaft moves in one direction from the central select position, one of the select springs is compressed thus generating a resilient force for returning the shift select shaft to the central select position, and when the shift select shaft moves in the other direction from the central select position, the other select spring is compressed thus generating a resilient force for returning the shift select shaft to the central select position.
However, since two springs are needed to maintain the shift select shaft in the central select position in the prior art, there are the problems that not only does the number of parts increase but also the length of the shift select shaft increases in order to provide space for placing the select springs.
The present invention has been carried out in view of the above-mentioned circumstances, and it is an objective of the present invention to both reduce the number of select springs used for maintaining the shift select shaft in the central select position and to shorten the overall length of the shift select shaft.
In order to achieve the objective, in accordance with the present invention a transmission gear shift system is provided which is a transmission gear shift system for selectively establishing a plurality of gear shift stages in which shift forks are operated by means of a shift select shaft supported on a transmission case, being moved in the axial direction according to a select operation of a shift lever and being moved in a circular manner according to a shift operation of the change lever. The shift select shaft is maintained in a central select position among three select positions in the axial direction by means of the resilient force of a select spring. A first spring seat and a second spring seat are supported in a slidable manner between a first stopper surface and a second stopper surface which are provided on the shift select shaft with a gap between them in the axial direction. The inner surfaces in the axial direction of the first and second spring seats are forced by the select spring in the direction in which they move away from each other so as to come into contact with the first and second stopper surfaces respectively, and the outer surfaces in the axial direction of the first and second spring seats are supported on first and second support surfaces respectively provided on the transmission case.
In accordance with the above-mentioned arrangement, when the shift select shaft is moved in one direction from the neutral position, since the first spring seat which is retained by the first stopper surface, moves together with the shift select shaft to move away from the first support surface and compresses the select spring against the second spring seat which is supported on the second support surface, and moves relative to the shift select shaft, the shift select shaft is forced towards the neutral position by means of the resilient force of the select spring. When the shift select shaft is moved in the other direction from the neutral position, since the second spring seat which is retained by the second stopper surface moves together with the shift select shaft so as to move away from the second support surface and compresses the select spring against the first spring seat which is supported on the first support surface and moves relative to the shift select shaft, the shift select shaft is forced towards the neutral position by means of the resilient force of the select spring.
Thus, since the shift select shaft can be forced from either direction to the neutral position by means of one select spring, not only can the number of select springs be reduced to a minimum, but also the overall length of the shift select shaft can be shortened by reducing the space required for placing the select spring.
Furthermore, in accordance with the present invention, a transmission gear shift system is provided wherein the first and second spring seats and the select spring are housed inside a breather chamber provided in the transmission case, and the first and second support surfaces are formed on the inner wall of the breather chamber.
In accordance with the above-mentioned arrangement, since the first and second spring seats and the select spring are housed by effectively using the internal space of the breather chamber provided in the transmission case, the space in which the first and second spring seats and the select spring are placed, can be minimized. Moreover, since the first and second support surfaces for supporting the first and second spring seats are formed on the inner wall of the breather chamber, special members for forming the first and second support surfaces are unnecessary and thus the number of parts can be reduced.